The production of conventional textile fabrics is known to be a complex, multi-step process. The production of fabrics from staple fibers begins with the carding process where the fibers are opened and aligned into a feedstock known as sliver. Several strands of sliver are then drawn multiple times on drawing frames to further align the fibers, blend, improve uniformity as well as reduce the diameter of the sliver. The drawn sliver is then fed into a roving frame to produce roving by further reducing its diameter as well as imparting a slight false twist. The roving is then fed into the spinning frame where it is spun into yarn. The yarns are next placed onto a winder where they are transferred into larger packages. The yarn is then ready to be used to create a fabric.
For a woven fabric, the yarns are designated for specific use as warp or fill yarns. The fiber or yarn packages (which run in the cross direction and are known as picks) are taken straight to the loom for weaving. The warp yarns (which run on in the machine direction and are known as ends) must be further processed. The packages of warp yarns are used to build a warp beam. Here the packages are placed onto a warper, which feeds multiple yarn ends onto the beam in a parallel array. The warp beam yarns are then run through a slasher where a water-soluble sizing is applied to the yarns to stiffen them and improve abrasion resistance during the remainder of the weaving process. The yarns are wound onto a loom beam as they exit the slasher, which is then mounted onto the back of the loom. Here the warp and fill yarns are interwoven in a complex process to produce yardage of cloth.
Coloring and shading are likewise complex processes in conventional textile production. Colors and patterns of color can be achieved by using yarns of various colors, resulting from the dyeing of the fiber or yarn packages themselves. Further, greige goods, yardage produced from undyed yarns, can be dyed in any of several ways common to the industry, such as jet dyeing, and vat dyeing. For application of color and patterns of colors onto the surface of a fabric, printing is commonly used, whereby pigments are applied to the fabrics by a series of engraved screens where each roll applies a specific color and part of the pattern.
Yarns and woven textiles have a history of being dyed with indigo dyestuffs. Indigo dye is a natural vat dye, but the use of natural dye has since diminished given that it has been synthesized. Indigo is called a vat dye as a result of the method of its application. Indigo is treated chemically previous to exposing a material to the dye within a vat. The process for dyeing traditional yarns and textile fabric with indigo is well known and is discussed in prior art U.S. Pat. No. 5,611,822; No. 5,484,457; and No. 3,457,022, incorporated herein by reference.
U.S. Pat. No. 5,611,822 describes a method of introducing a non-oxidizing gas into a chamber in order diminish or remove oxidizing agents in commercial indigo dyeing. The indigo dyed fibers of U.S. Pat. No. 5,611,822 can be natural or synthetic and include fibers in the form of garments or fabric, however the commercial dye apparatuses may need to be modified to provide a near airtight enclosed compartment capable of maintaining a non-oxidized atmosphere.
U.S. Pat. No. 5,484,457 illustrates another indigo dyeing method for textiles including nonwovens consisting of cellulosic blends. This particular method utilizes a water-soluble binder pervious to the application of the indigo dye. This is believed to be disadvantageous to durable coloration as some of the indigo dye can wash off to expose undyed areas or give otherwise poor fastness properties to the fibers.
U.S. Pat. No. 3,457,022 discloses a method of dyeing cotton yarn wherein the yarn is introduced to an indigo vat dye and then skyed or raised out of the dye and exposed to the air, but ultimately, once the yarn has been dyed to it's desired shade, the yarn must be woven into a fabric. This entire process is complicated and time consuming.
It is known to those skilled in the art, when dyeing yarn it is necessary to reduce the dyestuff in a solution of caustic soda, an alkali, and sodium hydrosulfite that then changes the dyestuff form from an insoluble paste to a soluble “leuco”. Leucos are those chemicals containing carbonyl groups, wherein the carbonyl groups become carboxyl groups in the presence of a reducing agent. When exposed to the caustic soda, the insoluble paste becomes a solution of sodium derivatives. The material is introduced to the solution and then skyed, or exposed to air. In the presence of air the solution is converted back to its insoluble stage and locks into the fabric as an indigo colored dye.
Conventionally, cotton yarns (usually in groups of 100 or so ends) are roped together and run through a large vat of this reduced indigo with several dips and nips. Once the yarn exits the vat, it is often squeezed and raised upwards (called skying) to allow the oxygen in the air to change the leuco back to the insoluble indigo dye. The shade is pale blue at this first stage. For deeper shades, another dyetank is used to repeat the imbuing, squeezing, and skyeing. Several of these tanks are placed sequentially to give anywhere from 2-3 dips for a light chambray, up to 8 dips for a dark denim shade. The yarns are rinsed, dried, and then merged together and slashed with a warp size agent and then beamed on a warp for weaving.
The production of nonwoven fabrics from staple fibers is known to be more efficient than traditional textile processes as the fabrics are produced directly from the carding process. Nonwoven fabrics are suitable for use in a wide variety of applications where the efficiency with which the fabrics can be manufactured provides a significant economic advantage for these fabrics versus traditional textiles. Hydroentangled fabrics have been developed with improved properties that are a result of the entanglement of the fibers or filaments in the fabric providing improved fabric integrity. U.S. Pat. No. 3,485,706, to Evans, hereby incorporated by reference, discloses processes for effecting hydroentanglement of nonwoven fabrics.
Most nonwoven fabrics are dyed either with pigments and binder systems, continuous, range dyed, printed, or jet dyed. This invention discloses a method for using a durable nonwoven fabric with a cellulosic content, preferably cotton, and running it through the same dyeing process as the yarn and getting a fabric with the same shade and visual aesthetics, but does not have to be slashed, warped, woven, or desized as seen with the prior art. Prior art signifies the need for a more rapid technique of creating indigo dyed fabrics. The present invention allows for rapid production of indigo dyed nonwoven fabrics and is beneficial to various industries since the resultant product is a roll good.